Hurricane JIMENA

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HURRICANE JIMENA DISCUSSION NUMBER 9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132009
200 PM PDT SUN AUG 30 2009
JIMENA CONTINUES TO HAVE A SMALL EYE EMBEDDED WITHIN A QUITE
SYMMETRIC CENTRAL DENSE OVERCAST. ON INFRARED IMAGES...THE EYE
TEMPERATURES HAVE WARMED SOMEWHAT...SUGGESTIVE OF ADDITIONAL
STRENGTHENING. SUBJECTIVE DVORAK T-NUMBERS REMAIN AT T 6.0 FROM
BOTH AGENCIES BUT OBJECTIVE T-NUMBERS SUPPORT A STRONGER HURRICANE
...PRIMARILY BECAUSE OF THE WARMER EYE. THEREFORE THE NHC INTENSITY
ESTIMATE IS BOOSTED TO 120 KT. ADDITIONAL STRENGTHENING IS
CERTAINLY A POSSIBILITY GIVEN THE WARM WATERS...LIGHT SHEAR...AND
MOIST TROPOSPHERE. HOWEVER...THE INTENSIFICATION PROCESS COULD ALSO
BE HALTED AT ANY TIME BY AN EYEWALL REPLACEMENT CYCLE. THE OFFICIAL
WIND SPEED FORECAST SHOWS ONLY A SLIGHT ADDITIONAL INCREASE IN
STRENGTH. BEGINNING AROUND 48 HOURS...THE GLOBAL MODELS SHOW
INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW NEAR JIMENA. THE
RESULTING INCREASE IN SHEAR WILL PROBABLY LEAD TO A WEAKENING
TREND...AND THIS IS REFLECTED IN THE OFFICIAL FORECAST. ALSO BEYOND
48 HOURS...THE INTENSITY OF THE TROPICAL CYCLONE WILL BE DEPENDENT
ON HOW MUCH IT INTERACTS WITH LAND.
THERE HAVE BEEN SOME TROCHOIDAL WOBBLES...TYPICAL OF THE MOVEMENT OF
INTENSE HURRICANES...BUT THE SMOOTHED INITIAL MOTION ESTIMATE IS
ABOUT 295/07. THE FUTURE TRACK OF JIMENA SEEMS TO DEPEND LARGELY
UPON THE EVOLUTION OF TWO MAIN FACTORS...A MID- TO UPPER-LEVEL LOW
LOCATED NEAR THE SOUTHERN BAJA CALIFORNIA PENINSULA AND A MID-LEVEL
RIDGE OVER THE SOUTHWESTERN U.S. AND NORTHWESTERN MEXICO. IF THE
LOW SHIFTS WESTWARD AND WEAKENS...IT WOULD ALLOW THE RIDGE TO BUILD
WESTWARD AND COULD CAUSE THE TRACK TO VEER WESTWARD AWAY FROM BAJA.
THAT APPEARS TO BE THE SCENARIO DEPICTED BY THE U.K. MET. OFFICE
AND ECMWF GLOBAL MODELS. HOWEVER...THOSE MODELS ARE THE WESTERN
OUTLIERS OF THE DYNAMICAL TRACK GUIDANCE. OTHER GUIDANCE SUCH AS
THE GFS...THE HWRF...AND THE GFDL INDICATE THAT THE MID- TO
UPPER-LEVEL LOW WILL CONTINUE TO INFLUENCE THE MOVEMENT OF THE
HURRICANE...SO THAT JIMENA WILL CONTINUE TO TURN TOWARD THE
RIGHT...AND MOVE NEAR OR OVER BAJA. THE OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS ONE AND IS CLOSE TO THE MIDDLE OF THE MODEL
TRACKS.
INTERESTS IN WESTERN MAINLAND MEXICO AND THE SOUTHERN BAJA
CALIFORNIA SHOULD MONITOR THE PROGRESS OF JIMENA. A HURRICANE WATCH
MAY BE REQUIRED FOR PORTIONS OF THE SOUTHERN BAJA CALIFORNIA
PENINSULA LATER TODAY OR TONIGHT.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/2100Z 16.6N 106.8W 120 KT
12HR VT 31/0600Z 17.3N 107.7W 125 KT
24HR VT 31/1800Z 18.7N 108.7W 125 KT
36HR VT 01/0600Z 20.6N 110.0W 125 KT
48HR VT 01/1800Z 22.6N 110.8W 115 KT
72HR VT 02/1800Z 26.5N 112.5W 75 KT...INLAND
96HR VT 03/1800Z 28.0N 114.0W 50 KT...INLAND
120HR VT 04/1800Z 28.5N 115.0W 25 KT
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FORECASTER PASCH
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